Exemplary embodiments of the present disclosure relate to a light emitting diode including a light emitting diode that includes electrode extensions for current spreading.
A GaN-based light emitting diode is applied to various fields including full color LED display devices, LED traffic signals, white LEDs, and the like.
A GaN-based light emitting diode is generally formed by growing epitaxial layers on a substrate such as a sapphire substrate, and includes an n-type semiconductor layer, a p-type semiconductor layer and an active layer interposed therebetween. In addition, an n-type electrode pad is formed on the n-type semiconductor layer and a p-type electrode pad is formed on the p-type semiconductor layer. The light emitting diode is electrically connected to an external power source through such electrode pads. Here, electric current flows from the p-type electrode pad to the n-type electrode pad through the semiconductor layers.
Generally, the p-type semiconductor layer has high specific resistance, causing uneven current spreading in the p-type semiconductor layer. As a result, current crowding can occur under the p-type electrode pad or on a side surface of the light emitting diode through corners or edges of the light emitting diode instead of flowing through an inner region thereof. Such current crowding results in reduction in luminous area, thereby causing deterioration in luminous efficacy. Thus, a transparent electrode layer having low specific resistance is formed on the p-type semiconductor layer in order to achieve current spreading. The transparent electrode layer having low specific resistance serves to spread electric current flowing from the p-type electrode pad before the electric current flows into the p-type semiconductor layer, thereby increasing the luminous area of the light emitting diode.
However, since the transparent electrode layer absorbs light, the transparent electrode layer is grown to a limited thickness and thus has a limitation in current spreading. Particularly, a light emitting diode having a large area of about 1 mm or more and generally used for high power output has a limitation in current spreading through the transparent electrode layer.
Moreover, since electric current flows to the n-type electrode pad through the semiconductor layers, current crowding is likely to occur in a region of the n-type semiconductor layer in which the n-type electrode pad is formed. This means that electric current flowing through the semiconductor layers crowds near the n-type electrode pad. Therefore, there is a need for solving the problem of current crowding in the n-type semiconductor layer.